The present invention relates generally to transport devices used with agricultural machinery and more particularly to transport devices for grain drills.
As with most agricultural machinery designed to be pulled by a tractor, a conventional grain drill has its longer dimension oriented perpendicular to the direction of operational movement. For descriptive purposes the longer axis of a grain drill is hereinafter referred to as the longitudinal axis and the shorter axis, which is parallel to the direction of plowing, is referred to as the transverse axis. Often a number of grain drill units are connected lengthwise for the purpose of increasing the amount of ground treated in a plowing pass. When units are interlinked, the length to width ratio of the apparatus being pulled is greatly accentuated.
Most grain drills have a row of openers for piercing the ground and opening a furrow, followed by a row of press wheels which close the furrow after the grain has been deposited. The press wheels have a fixed common axis oriented parallel to the longitudinal axis of the apparatus which allows the wheels to roll in the direction of plowing.
During typical farming operations, it is often necessary to move a grain drill apparatus from field to field or along the roadway between fields. Because of length of the apparatus, it must be transported in a direction perpendicular to the direction of plowing movement operations. To avoid damage to the press wheels during transport, it is necessary to elevate the drill press and provide longitudinally oriented transport wheels. A number of devices have been used to accomplish this result with varying degrees of success. Most transport devices utilize a heavy wheel mounted frame attached about the periphery of the drill. The frame may be lowered with respect to the drill, thereby raising the drill to accomodate transport. Several problems arise with this type of transport device, especially when used with multiple unit drills. The transport frame is expensive to produce and also adds a considerable amount of weight to the drill press. This added weight changes the operating characteristics of the drill press, which may render it unusable in wet fields. Another problem with the frame type structure occurs because the drills must often be pulled over irregular ground, such as road ditches and terraces. A long rigid frame, when encountering such obstacles, tends to twist and bend and may also cause the drill press to become high centered. Thus, a more flexible transport device is desirable.
Another means of providing transport has been to use transport wheels which are mounted directly on the drill press housing. Such devices avoid part of the weight problem encountered with a transport frame apparatus, but experience problems with structural integrity. In devices now available, each transport wheel is generally extended on a single, pivoting arm that is attached to a heavy mounting framework which must be added to the drill press. Such mounting has proved to be unsatisfactory due to the stresses experienced by the wheels during normal transport operations. Because of the extreme length of most drill press devices, wheels experience a side thrust directed perpendicular to the path of longitudinal travel whenever the apparatus is forced to make a short radius turn. This side thrust tends to bend and displace the transport wheel mounting. A similar effect is produced by longitudinal forces on the wheel which are encountered when the wheel falls into a chuck hole or the like. A problem also arises from vibrations set up in the pivot arm which acts as a lever and causes bending and metal fatigue in the mounting framework and drill frame. Finally, a problem with high centering, similar to that experienced with a rigid transport frame is also experienced with housing mounted transport wheels since with present inventions, the individual grain units are prevented from flexing by the field hitch while in the transport mode.
It can therefore be seen that a need exists for a grain drill transport device which is light in weight and which allows a degree of vertical and rolling displacement between individual drill units to accomodate transportation over irregular ground. The device should be capable of sustaining longitudinal and transverse forces experienced by the transport wheels without bending or deformation. The device should also be capable of being quickly deployed to save operating time.